Stent device for performing endovascular repair of aneurysms

ABSTRACT

A blood vessel wall-defining device for repairing an abdominal aneurysm. The device comprises a percutaneously-insertable structural frame extending between first and second ends having an unexpanded diameter which is smaller than the diameter of the blood vessel to permit the structural frame to be placed into the blood vessel. The structural frame being expansible to form a cylindrical structural skeleton having a slightly larger diameter than the blood vessel to facilitate the securing of the skeleton in position in the blood vessel. The skeleton has a sheath of a tubular fabric. The said structural frame has a plurality of spaced coiled stents prior to expansion which are uncoiled under the aegis of a balloon catheter and locked into position by ratchet means.

BACKGROUND OF THE INVENTION

This application is by the same inventor, filed Jun. 21, 1996 under U.S.patent application Ser. No. 08/667,604, now U.S. Pat. No. 6,015,430 andis incorporated herein in its entirety.

This invention relates generally to blood vessel wall definingtechniques and more specifically to a device and method capable ofrepairing aneurysms in large vessels employing percutaneous insertion.

Approximately 70% of the aneurysms reported in the United States eachyear are repaired by the conventional open surgical technique known asaneurysmectomy. However, the mortality rate associated withaneurysmectomy remains relatively high, 12.9% for elective surgery,30-50% for emergency surgery after vascular rupture, and as high as 71%for patients over 70 years of age (Ruckley, In: The Cause and Managementof Aneurysms, Greenhalgh R. M. et al. ed, W. B. Saunders, Philadelphia,p. 327-337, 1990; Lawrie et al, Surgery 85:483, 1979). Some of thefactors involved in the high operative mortality rate are underlyingcoronary or cerebral atherosclerosis, severe obstructive pulmonarydisease, and renal disease.

Another major disadvantage of aneurysmectomy is that, because of thenature of the operation, it can only be performed in medical facilitieswhich have the sophisticated equipment necessary to perform majorcardiovascular surgery. In cases where the prognosis for rupture isimminent, fatalities may occur because of insufficient time to performdiagnostic studies and/or transfer the patient to a major medical centerwhere surgery can be performed. Therefore, there has been a long feltneed for simpler, quicker and less traumatic techniques for repairinganeurysms.

Percutaneous techniques of blood vessel repair such as introducingvascular stents into arteries or veins have been suggested, and have hadsome significant applications, but known approaches have certaindrawbacks and/or limitations and thus, have not found wide use withrespect to large vessels, especially the abdominal aorta where asignificant number of aneurysms occurs. Furthermore, it should also beborne in mind that the stents conventionally employed to open cloggedarteries are quite different from an abdominal aneurysm stent, thelatter often times has to deal with an aorta that is out of roundcross-section wise because of the lesion area on the aorta.

Of late, the prior art workers have expended considerable efforts in thearea of affecting repair of aneurysms of an abdominal aorta by speciallyfabricated stents. These efforts have led to the issuance of quite a fewU.S. patents, namely:

U.S. Pat. No. 5,211,658 to Clouse

U.S. Pat. No. 5,360,443 to Barone et al

U.S. Pat. No. 5,387,235 to Chuter

U.S. Pat. No. 5,456,713 to Chuter

U.S. Pat. No. 5,522,880 to Barone et al

U.S. Pat. No. 5,562,726 to Chuter

U.S. Pat. No. 5,571,173 to Parodi

U.S. Pat. No. 5,676,697 to McDonald

U.S. Pat. No. 5,683,452 to Barone

U.S. Pat. No. 5,693,084 to Chuter

U.S. Pat. No. 5,755,777 to Chuter

U.S. Pat. No. 5,843,160 to Rhodes

The subject matter of these patents are incorporated herein byreference.

The present invention builds on the prior work of the instant inventorW. Henry Wall as exemplified in U.S. Pat. Nos. 5,192,307, 5,824,038 and5,843,163. The prior material is incorporated herein.

SUMMARY OF THE INVENTION

The present invention provides a blood vessel wall-defining device; anda method for insertion of the wall-defining device within a blood vesselof an animal, preferably a human patient, which has an abnormalwidening, or aneurysm, along a section of the vessel wall. The insertionis particularly applicable to aneurysms in an aorta, especially in theabdominal aorta below the confluence with the renal arteries and abovethe bifurcation of the aorta into the common iliac arteries.

According to a first aspect of the invention a blood vesselwall-defining device for repairing an aneurysm comprises in combination,a percutaneously-insertable structural frame extending between first andsecond ends having an unexpanded diameter which is smaller than thediameter of the blood vessel to allow the structural frame to bepercutaneously placed into the blood vessel, the structural frame beingexpansible to form a generally cylindrical structural skeleton having aslightly larger diameter than the blood vessel to facilitate thesecuring of the structural skeleton in position in the blood vessel.

The structural frame includes a plurality of flexible elongated rodswhich are equidistantly affixed to a sheath of fabric constructed of athermoplastic material such as nylon. The sheath has a tubularconfiguration. Prior to percutaneous placement, the tubular cylinder isin undistended accordian-like folds to present a diminished diameter.The rods may be constructed of a bio-compatible metal or plastic.

Internally of the sheath are a series of displaced ring stents of athermoplastic material or a bio compatible metal having a memory. Thesering stents are coiled upon themselves to present a smaller diameterwhich upon uncoiling will provide an enlarged annular configuration. Thecoiled ring stents are retained in a coiled-up condition by an elongatedpin which upon successful placement is retracted to permit uncoiling ofthe ring stents. The uncoiling of the ring stents provide the mechanicalmeans to unfold the sheath or tube of fabric material to which theflexible metal or plastic rods are equidistantly attached.

In one embodiment, the ring stents, when constructed of a metal having amemory, would ordinarily recoil except that the end portions areprovided with a ratchet locking means that retains the ring stent in itsuncoiled position and therewith resistant to re-coiling. The ratchetmeans may be of a selected number whereby the stent ring means may beopened and progressively held at various uncoiled positions but cannotrevert to a coiled position. The ratchet locking means is similar to theone disclosed in said parent application Ser. No. 08/667,604, filed onJun. 21, 1996.

Due to the fact the device is relatively long the stent may underordinary circumstances cover openings to branch arteries. In such acircumstance, it has been found useful to have certain portions of thedevice devoid of the tube of fabric material or sheath whereby blood mayeasily pass through the spaces between the rods of the device of thepresent invention.

As stated in another way, the ring stent provides a direct impingementon the flexible metal or plastic rods, i.e. without the presence of thefabric material or sheath.

It is contemplated that the device of the present invention may bepositioned not only in the abdominal aorta but also in smaller brancharteries. In such a situation the diameter of the resulting device maydescribe a smaller diameter. The device can have a tube of fabricmaterial or sheath throughout.

In another embodiment, the device for percutaneous insertion is carriedby a known type of balloon catheter in a folded condition. The ringstents are in a coiled-up condition which upon successful placement ofthe device of the present invention the balloon is then inflated. Thepressure of the balloon internally of the ring stent uncoils the stentwhich in turn impinges on the rod carrying fabric tube or sheath therebyunfolding the sheath and spacing the rods appropriately. The rods andsheath are detailed to abut and define the vessel wall of the artery.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a perspective and diagrammatic view of the stent device of thepresent invention in place in an abdominal aorta;

FIG. 2 is a fragmentary end view of the stent prepared for mounting;

FIG. 3 is a cross-sectional view of the stent prior to being expanded;

FIG. 4 is a cross-sectional view of the stent in an expanded condition.

FIG. 5 is a perspective of the device showing the retaining means forthe individual ring stents.

DETAILED DESCRIPTION OF THE INVENTION

Attention is now directed to FIG. 1 for a general view of the stent 10of the present invention which is designed to be fitted into theabdominal aorta artery 11 in the area bordered at the top by the leftrenal artery 12 and the right renal artery 13. At the bottom, it isdefined by the bifurcated left iliac artery 14 and the right iliacartery 15. The left and right renal arteries supply blood to the leftkidney 16 and right kidney 17, respectively.

The abdominal aorta 11 may have an aneurysm or a ballooning out that maytake various forms; suffice it to say that it is an outcropping of thewall of the aorta 11 resulting in a considerable weakening of the aortawhich may lead to a rupture.

Such weakening will have little or no affect on the patient until itactually bursts and may not be known to exist. Sonograms can detect theaberration in wall disfiguration and outcropping. FIG. 1 shows anexpanding aorta. Upon the bursting of the aorta's wall, the patient willbleed internally often to a point of death.

The stent shown in FIG. 1 is fabricated of a skeleton of elongatedflexible metal rods 20 which are shown to be eight in number. It iscontemplated that the number of rods may be greater or lesser in number,eight is preferred which are equidistant from each other whenpositioned.

The metal rods 20 are secured to a sheath 21 of fabric material whichmay elongatedly extend the entire length of the device or may terminateso that there is an open portion 22 while the rods 20 extend for anadditional distance. The area unencumbered by the sheath provides fluidaccess between the rods so that branches off the abdominal aorta aresupplied with blood.

Internally of the tube and rods is a series of ring stents 25. Thesering stents are coiled prior to percutaneous insertion and are uncoiledunder the aegis of a balloon carried by a catheter in one embodiment or,in another embodiment, automatically when a retaining pin is retractedfrom the ring stents and the latter are constructed of coiled metalhaving spring qualities.

FIG. 2 is a fragmentary view showing a diagrammatic view of the sheath21 in an expanded condition with rods 20. The expansion is achieved byuncoiling ring stents 25 in either of the embodiments, both of which areshown in FIG. 2.

A catheter 31 is shown in a fragmentary fashion which is the carryingmeans for the implantation of the device. The FIG. 2 shows only a few ofthe ring stents 25 which are in a coiled position again. The ring stentsare provided with a locking means which includes an elongatedretractable pin 32 which is withdrawn from its locking position when thedevice 10 of the present invention is in place whereby the stent springsopen, as stated, under its own accord when the stent is constructed of amaterial that has a spring memory whereby to assume an uncoiledconfiguration. When the ring stent, in the other embodiment, does notpossess spring qualities, the unfurling must be assisted by means of aballoon in the catheter 31. To accomplish this the catheter 31 has anelongated balloon 33 which is conventional to a balloon catheter and isnormally employed to open a blocked artery. In this instance it isdetailed to assist to unfurl the ring stent 25 and thereby the stent 10of the present invention by inflating the balloon 33 to a desiredposition.

FIG. 3 shows a cross-section of the stent 10 of the present invention ina conventional tubular member 35 prior to percutaneous disposition inaorta being afflicted by an aneurysm.

Note therein the folded-up sheath tube 21 and the coiled ring stent 25.The latter has a conventional plural ratchet locking means 34 forlocking the ring stent 25 at selected positions in the progressivelyuncoiled position once the ring stent 25 has been expanded by balloon 33supplied in a catheter 31.

In FIG. 4, one can view the cross-sectional view similar to that shownby FIG. 3 where the balloon 33 has uncoiled the ring stent 25 to itsfullest position which is to the point of locking the ratchet lock orlocks 34 as depicted. The ring stent in turn abuts outwardly radiallyagainst the sheath or fabric tube 21 with the attendant metal rods 20.

Attention is now directed to FIG. 5 which depicts another embodiment ofthe abdominal aortic stent system and shows the disposition thereof. Aspecial single rod 20A of the rods 20 carries a plurality of ring stents25 in a fixed spaced relationship. Each of the ring stents 25 has acompressible loop 25A through which the rod 20A is positioned.Securement is accomplished by compressing the loop 25A about the rod20A. It is contemplated that a suitable adhesive may accomplish thesecuring of the said rod 20A to the ring stent 25. As in one of theforegoing embodiments the insertable balloon catheter 31 has anattachment 36 adapted and constructed to slide along an elongated sliderail 32A which has a distal attachment stop means 30 which is attachedto the distal end portion of the rod 20A and, as stated, to which thering stents 25 are attached. Another attachment means 37 is secured tothe rod 20A to which the ring stents 25 are attached at its proximateend portion and radially to the slide rail 32A.

The catheter, surrounded by a conventional tubular member 35, is used tomove the unfurled and undisposed stent 10 through the to-be treatedaorta to a position opposite the aortic lesion. When properlypositioned, the tubular member 35 is withdrawn. Then the slide pin 32 iswithdrawn from the stent 10 and the lead ring stent 25. After all of thering stents 25 have been permitted to uncoil and held in theirrespective places by retaining means, pin 32 is withdrawn from itsattachment means 24 and removed with the catheter. It is contemplatedthat the catheter retracts from ring stent to ring stent.

In the case of employing ring stents that do not unfurl of their ownaccord, a balloon catheter is employed in a known manner. The balloon 33is inflated to uncoil the lead ring stent 25, that is, as stated afore,when the stent is constructed of a material that wants to stay coiledand must be locked open to a position of abutment against the sheath 21and in turn against the inner wall of the aorta. The lead ring stentremains locked open by the ratchets; the balloon 33 may be thendeflated. The balloon catheter is withdrawn sliding along a guide rail32A which acts as a guide for the balloon catheter so that the ballooncan be reinflated at the next ring stent. In some embodiments it may bedesirable to employ a balloon that has a suitable dimension thatencompasses more than one ring stent 25 at a time.

The sheath 21 is attached to the rods 20 or ribs as discussedheretofore. Of course provision must be made for openings in the sheath21 whereby the said loops 25A of the individual ring stents 25 mayprotrude therethrough.

One may construct various standardized sizes of the structural skeletonand thin walled flexible tubular member 35 for packaging into kits foruse in the present invention.

The devices 10, as stated, may be preinstalled in the distal ends ofrespective catheters and may be injected by pusher devices similar tothose employed to eject vena cava filters and the like. As stated,devices 10 are constrained by a tubular member 35, which may be a knowndelivery sleeve.

The distal ends of the rods 20 are rounded to hinder any undue abrasionagainst the aorta.

Various other modifications of the invention, within the spirit thereofand the scope of the claims, will occur to those skilled in the art.

What is claimed is:
 1. A blood vessel wall defining device for repairingan aneurysm comprising in combination, a percutaneously-insertablestructural longitudinal frame extending between a first end and a secondend having an unexpanded diameter which is smaller than the diameter ofsaid blood vessel for said structural frame to be percutaneously placedinto said blood vessel, said structural frame being expandable to form agenerally cylindrical structural skeleton having a slightly largerdiameter than said blood vessel to facilitate the securing of saidstructural skeleton in position in said blood vessel, said structuralframe including a plurality of longitudinal support rods, said supportrods being attached to a tubular sheath for at least a portion thereof,a plurality of expandable ring stents longitudinally displacedinternally of said tubular sheath, said ring stents prior to use areheld in a coiled position by an elongated retractable pin having acoiled smaller deployment diameter prior to use and an expanded diameterin the uncoiled position.